Test of electronic devices is needed to insure that they meet specifications. Test systems can be very very expensive because they must be capable of very high speed operation, very precise time and voltage and current measurement, and must be able to handle devices with hundreds and hundreds of connections. To be able to handle different devices, a load board is often fabricated to connect a device under test (DUT) to the tester. These DUT boards are also very very expensive.
A tester generally has two major categories of electronics that can connect to a pin, a tester pin which can drive or receive a signal and measure such (often called a channel, or test channel, or tester channel, or measurement channel), and a device power supply (DPS) for powering the device. The test channel is often denoted as TC.
Tester channels and device power supplies are very different in their capabilities. Device power supplies can provide large amounts of power but are limited in speed of operation (e.g. slew rate), for example. Tester channels on the other hand cannot handle much power but are capable of high transition speeds, accurate measurements, etc.
Additionally, a tester is often used to test more than one of the same part at a time. It may have several test sites for testing devices, for example, four parts may be tested at the same time (DUT1, DUT2, DUT3, DUT4). Thus the number of tester channels and device power supplies is increased.
Commonly a tester has many more tester channels that device power supplies. Device power supply cards can be very expensive, for example, $90K/card.
When a device needs more power supplies than a tester has, this presents a technical problem which needs a technical solution.